Conventionally, the filler cap for the fuel tank of an internal-combustion engine is provided in the automobile that is required to draw an atmosphere therein by the volume corresponding to a fuel consumed in the fuel tank. For such drawing, an air passage for drawing the atmosphere is provided in the filler cap.
For this reason, when the fuel tank provided in the automobile etc. inclines at more than a predetermined angle, there was a danger of the fuel leaking from the air passage and catching fire.
When the fuel tank inclines at the predetermined angle, this filler cap can securely suppress the inconvenience that the fuel in the fuel tank flows out of the air passage provided in a main body of the filler cap.
With the fuel tank inclined at the predetermined angle and the fuel flowing into a cylinder main body, when a float constituting a valve mechanism portion provided in the air passage floats externally, a sphere also constituting the valve mechanism portion is pressed on a reduced-diameter portion of the cylinder main body by the float, thereby closing the air passage. However, in the state where the above fuel tank is not inclined, harmful gas evaporated from the fuel may be discharged to an exterior of the fuel tank from a gap existed between a piston and an inner surface of the cylinder main body. This harmful gas has a problem of causing environmental pollution that leads to difficulty in a consumption improvement of the fuel.